ABSTRACT
E wing’s sarcoma of bone was originally identified by James Ewing in 1921 as a tumor o f long bones, distinct from osteosarcoma, sensitive to radiation and of possible endothelial origin. Subsequently, Ewings sarcoma was observed in all types of bones and also in soft tissues. Its histogenetic origin is now suspected to be neural, a pheno typic characteristic which links Ew ings sar coma to a more differentiated tumor known as peripheral primitive neuroectodermal tumors (PPNET) or neuroepithelioma. This link is further supported by the observation o f iden tical chromosome translocations in both types o f tumors. The presence o f these alterations has provided the unifying criteria for these tumors with variable tissue localization and cell differentiation, now collectively designated as the Ewing family o f tumors. Given that these malignancies are highly suspected not to be o f mesenchymal origin, Ewing tumor appears more appropriate than Ewings sarcoma to term these neoplasia. Molecular characterization of these translocations has led to new strategies for diagnostic and staging o f patients and has also opened new prospects to our understanding of the biology of this tumor.
